fulltext - DiVA

The high-alpine region 267as a predominant or at least as a physiognomicallywell marked species. Quite often it is found in awelldeveloped, soaked carpet of mosses (Philonotisfontana, Webera albicans). The northern unicentricRanunculus sulphureus displays a similar ecologicalbehaviour, but it is very rare in Northern Sweden(the Tornetrask area).Related to the Ranunculus nivalis communities,but with a somewhat later exposure are the communitiescharacterized by Phippsia algida. Theyare mostly found in the middle-alpine region, usuallycovering only small areas, depending upon irrigationduring the entire season. The Phippsia communitiesare often subject to erosion and appearas open vegetation. In some extreme places Phippsiaalgida stands as the only vascular plant in the wetgravel surrounded by small cushions of mosses.LUZULION ARCTICAE .-At high altitudes a specialtype of snow-bed vegetation. occurs in places witha late exposure, but not necessarily with a verythick snow cover. The ground consists of moist,gravelly soil, more or less influenced by solifluction,and for some time, at least, by irrigation. Characteristicspecies are Luzula arctica and Saginacaespitosa (alliance Luzulion arcticae). Also the rareStellaria crassipes should be mentioned. Thisalliance is rich in species, but none of them ispredominant.In Torne Lappmark the former glacial cirque ofMt. Nissontjarro offers a good opportunity ofstudying the different sociations of the alliance.Another good locality with abundant Saginacaespitosa is Mt. Kerkevare in the Sarek Mts. AlsoMt. Paltsa should be mentioned.DISTICHION CAPILLACEI.-As is the case in soilspoor in lime, one will also on calcareous soils findextremely late exposed communities in whichvascular plants are unable to exist. These communitiesare not exposed until well into July, andeven though they are not always constantly irrigated,they will remain very wet. Accordingly,there is no reason to distinguish between one heathand one meadow series, even more inappropriatehere than on soils poor in lime, for the calcareoussoils retain water to a higher degree than do silicioussoils.Though the areas devoid of phanerogams arefairly small quite a number of bryo-species maybe predominant. Important species are Weberacommutata, W. albicans, Calliergon sarmentosum,and Distichium capillaceum (alliance Distichioncapillacei). Also several Marchantiaceae may occuras pioneer plants on "new" soil (Peltolepis grandis,Asterella lindenbergiana). In places with a regularsupply of ice-cold water W ebera albicans forms oneof the most distinctive communities deficient invascular plants.THE HIGH-ALPINE REGIONBy Olav GjrerevollThe border between the middle-alpine and the highalpine regions is based on the upper limit for coherentvascular vegetation. This means that in thehigh-alpine region only scattered occurrences ofplant communities are found. Lichens and somewind-hardy bryophytes grow on exposed rock andgravel. But most of the vegetation that still occursis of snow-bed character, consisting mainly ofcommunities of Salix herbacea, Ranunculus glacialis,and bryophytes.18- 652151 APhS 50The summer is invariably short, even thoughthe snow cover may not be particularly thick inmany places. However, large areas are taken upby perennial snow fields or glaciers. Deposition ofice sheets on the ground or on the snow surface,derived from the moisture of clouds striking thesummits, is a common phenomenon, and fresh snowmay fall at all seasons. The average temperatureduring the summer months is low, only a fewcentigrades above freezing..Acta Phytogeogr. Suec. 50